Why is my gameplay so jerky even after upgrading?

[Kyoujin]

Old specs:
AMD Athlon 1.3ghz
AMD 761 mobo
640mb pc2100 DDR ram
nVidia GeForce 2 Ultra

New specs:
AMD Athlon XP 2600
Gigabyte K7 Triton KT600
768mb pc2100 DDR ram
ATI Radeon 9600pro 128mb Cat 3.9

Adelphia cable internet. 300kbps max speed.

With very little tweaking my FFXIbench2 is 3750H.

With both my old and new setup I get laggy, jerky gameplay. i.e. every third second my video slows to create the effect of the screen being jerked by.

Can anyone help me out with this?

[Oni5115]

Have you tried the 3.7 catalyst drivers? I heard other people with Radeon cards say those worked the best. Although I've also heard that 3.7 and 3.9 worked. I would suggest trying the 3.7 just to see if that works better for you.

[Altimit]

Game plays really jerky one my PC too, only I have an nVidia card. I've tried all the nVidia drivers so I'm inclined to beleive that its not related to that card at all. You should still try different ATI driver just to see though.

[ShakyJake42]

Make sure DMA is enabled for your hard drive. If this is off, it would create really jerky performance.